1. Field of the Invention:
This invention relates to reel drive devices in mechanisms for running a tape-shaped medium between two reels.
2. Description of the Prior Art:
In the past, in the mechanism for running a tape-shaped medium between two reels, when braking the rotating reel, for example, in a recording and reproducing apparatus such as VTR or tape recorder for audio, the rotation of a take-up reel support table was stopped, and, at the same time, a pad or the like was pressed against a supply reel support table with a constant force by a mechanical braking device such as a plunger. Thus, the rotation of the reel was braked.
Also, in the tape-shaped medium running mechanism of the so-called direct drive in which the take-up reel support table and the supply reel support table were directly driven by respective separate motors, when stopping the running of the tape-shaped medium, the rotation of the reel was braked in such a manner that the take-up reel support table drive motor was stopped, and, at the same time, the supply reel support table drive motor was caused to produce a prescribed torque in the reverse direction to that it has so far been rotated.
Also, in the above-described direct drive type tape-shaped medium running mechanism, on the basis of information signal obtained by converting the tension information of the tape-shaped medium to an electrical signal by electrically detecting the state of a tension arm, or by detecting the rotation period of the reel, a control signal, corresponding to the tension state and rotation period, was generated by a computation circuit or the like, and the reel support table drive motor was controlled by that control signal to control the rotation of the reel.
In these conventional methods, the braking force was not controlled in accordance with the rotating state of the reel. Since, while the rotating state of the reel was ever changing in correspondence to the amount of the tape-shaped medium convoluted on the reel, the rotation of the reel was controlled by a constant reverse torque produced by the rotation drive means for the reel, particularly when the reel was rotating at a high speed, a rapid braking resulted. So by the inertia of the reel or the shock of the braking, damage, for example, elongation and loose, sometimes happened to the tape-shaped medium convoluted on the reel. For example, in the recording and reproduction apparatus or the like, the use of the conventional methods has become an obstacle to an attempt to perform a long time recording or reproduction by thinning the thickness of the tape-shaped medium.
Also, in case the rotation of the reel was controlled by using the conventional method, when the computation circuit or the like was used for producing a control signal for controlling the rotation of the reel, the computation had to be carried out every time new information of the tension state of the tape-shaped medium and the rotation period of the reel entered the computation circuit. So, the structure has become complicated, and the cost increased.